Physiology, Health & Exercise

Lesson 18 Normal BGLPathology of diabetes mellitus (DM)

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Normal BGL & Diabetes

Includes: Role of insulin & glucagon Pancreas & changes in BGL Non-insulin dependent diabetes mellitus

(NIDDM) Insulin dependent diabetes mellitus

(IDDM)

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Normal Blood Glucose levels

Glucose- source of energy for body Carbohydrates digested to glucose Absorbed by blood capillaries in villi Carried to liver by hepatic portal vein Then distributed to body cells

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Normal Blood Glucose levels

If too much glucose (hyperglycaemia) in blood: Why does this happen? How does the body respond? BGL monitored by receptors in Islets of

Langerhans (pancreas) Respond by stimulating an enzyme that

promotes production of insulin (by cells) Excess glucose stored as glycogen by liver BGL fall back to normal levels

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Normal Blood Glucose levels

If glucose levels in blood drop (hypoglycaemia): Why does this happen? How does the body respond? BGL monitored by receptors in Islets of

Langerhans (pancreas) Respond by stimulating an enzyme that

promotes production of glucagon (by cells) Glycogen converted into glucose by liver BGL increase back to normal levels

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Normal Blood Glucose levels

Example of homeostasis1. What does this mean?2. Why is it described as being negative

feedback?

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Normal Blood Glucose levels

Insulin can affect a number of different cell types, principally:

Skeletal muscle cells Liver cells Fat cells

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Normal Blood Glucose levels

Skeletal muscle cells & fat cells have very low permeability to glucose in absence of insulin

Insulin acts by stimulating the uptake of glucose into muscle cells

Liver cells are quite permeable to glucose, so glucose enters whether or not insulin is present

But insulin still increases uptake of glucose by liver cells & glycogen formation

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How does insulin act?

Insulin is a protein hormone Extracellular hydrophilic 1. Binds to specific insulin receptors in cell

membrane of target cell2. Activated receptor promotes recruitment

of glucose transporters from intracellular pool to cell membrane

3. glucose transporters increase insulin- mediated uptake of glucose into cell

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How does insulin act?

4. When insulin levels decrease, glucose transporters move from cell membrane to intracellular storage pool, where they can be recycled

Under certain circumstances e.g. obesity, number of insulin receptors decreases

Glucose uptake by cell decreases Leads to insulin resistance

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How does insulin act?

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Types of diabetes mellitus (DM)

Two types:1. Type 1- Failure of pancreas to produce

adequate quantities of insulin IDDM (insulin dependent DM)

2. Type 2-Failure of tissues to respond to insulin (insulin resistance) NIDDM (non-insulin dependent DM)

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Type 1 or IDDM

Accounts for 5-10% of diabetes cases Caused by destruction of some or all -

cells in Islets of Langerhans Inadequate insulin production Commonly occurs in childhood Previously called early-onset or juvenile-

onset diabetes

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Type 2 or NIDDM

Much more common Accounts for 90-95% of diabetes cases Previously called late-onset because more

common in people over age of 40 However becoming more common in

younger people (and has been diagnosed in people as young as 13!)

More than 80% of people with NIDDM are overweight

Obesity is the greatest risk factor for NIDDM

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Type 2 or NIDDM cont…

Can produce insulin Have insulin levels in blood normal or

higher than normal But target cells (especially in liver &

skeletal muscles) have become less sensitive to insulin

Insulin resistance Deficiency of insulin receptors Cells less able to take up glucose BGL rise

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Type 2 or NIDDM cont…

In this case most people develop Insulin resistance before they develop diabetes

Pancreas tries to compensate by producing more insulin

Eventually the -cells become “worn out” Insulin production decreases Causes an increase in BGL